Passive Leg Press: New Device Increases Muscle Power

A new research study investigated the effects of 10 weeks of passive leg press training on jumping performance, speed, and muscle power. Passive leg press training (PLP) was developed based on the concepts of the stretch-shortening cycle and the benefits of high muscle contraction velocity. In PLP training an athlete stands on a platform and the machine allows the leg muscles to apply a maximum downward force against a plate moved up and down at a high frequency by an electric motor. The leg muscles are able to accomplish the concentric and eccentric contractions in a passive, rapid, and repetitive manner.1

30 male college students who had not performed any resistance training in the previous 6 months were chosen to participate in the 10 week study. Participants were randomly assigned to a traditional resistance training group, a low-frequency PLP training group, or a high-frequency PLP training group. Each training protocol was performed 3 times a week for 10 weeks. Before and after the 10-week training, the vertical jump, drop jump, 30-meter sprint, explosive force, and stretch-shortening cycle (SSC) efficiency were tested for each member of the study. After the participants performed 5 squat jumps and a counter movement jump measurement (CMJ), the SSC efficiency was calculated using the height ratio of squat jumps and CMJ.2

A Smith machine was used as training equipment for the traditional group, and the squat movement frequency was controlled at 0.5 Hz (using a metronome). The training load was 70% of the participants’’ one-rep max, and was adjusted midway through the study. A PLP machine was used for both the low and high frequency PLP training groups, and had a controlled movement frequency of 0.5 Hz and 2.5 Hz respectively. Each session of the PLP training group lasted 20 seconds, and the force that was exerted was required to remain above 70% of their one-rep max.3

The results of the study revealed that high-frequency PLP training significantly increased vertical jump, drop jump, 30-meter sprint time, instantaneous force, peak power, and SSC efficiency. The low-frequency PLP training group experienced significant increases in vertical jump, 30-meter sprint time, instantaneous force, and peak power. The changes in the high-frequency PLP training group were significantly better than the traditional resistance training group. The traditional resistance training group only saw an increase in 30-meter sprint performance and peak power.4

The findings of this research study indicate that jump performance, speed, and muscle power can be significantly improved after 10 weeks of PLP training at a high movement frequency. This type of training is unique method to use to enhance performance. Athletes may find this new method useful in particular if they want to develop faster contraction velocity.